As nowadays many people have difficulties in maintaining good health due to stress and irregular meals in our complex society, it is very common for people to die from malignant tumors, i.e., cancer. Since the risk of cancer has constantly increased, effective counter measures are strongly needed. Therefore, recently, methods of treating cancer, and in particular, radiotherapy, have become important points of interest.
Two core elements are necessary for successful radiotherapy on tumors. First, radiation is required to be precisely applied to a tumor, and second, a planned radiation dose should be identical to a radiation dose which is actually applied.
A variety of displacement errors must be reduced in order to precisely apply radiation to a tumor. Displacement errors caused by a patient's body may be classified into three categories: a position related organ motion error, a gap fraction organ motion error, and an internal fraction organ motion error.
The position related organ motion error occurs due to changes in positions of a patient's internal organs according to a patient's posture, such as standing or lying down, while the patient is being treated. The position related organ motion error may be reduced by considering in advance the patient's posture for treating the patient and planning a treatment position.
The gap fraction organ motion error occurs due to changes in positions of a corresponding organ and its neighboring organs according to the filling degree of the bladder, rectum, or stomach. The gap fraction organ motion error may be removed by ensuring that the patient's condition during treatment planning and the actual treatment is the same.
The internal fraction organ motion error occurs due to changes in positions of a corresponding organ and its neighboring organs according to breathing or heartbeat. The internal fraction organ motion error is of physiological nature and occurs frequently in any living body. In particular, breathing has a significant effect and thus the internal fraction organ motion error is a serious problem affecting organs influenced by diaphragmatic respiration. Thus, the internal fraction organ motion error may be removed by tracing an external anatomic motion according to the patient's breath and applying radiation only to a specific part of an internal organ according to a change in a position of the specific part.
The inventors of the present invention have invented devices disclosed in Korean Patent Nos. 0706758 and 0740340.
However, if the above devices are used to apply radiation to a patient's portion to be treated, a radiation opening and closing device is opened only when an organ is at a specific position, which increases a time taken to actually treat the patient.
Meanwhile, in order to apply radiation to a patient's portion to be treated, a shield for protecting a normal tissue of the patient is manufactured and attached to a radiotherapy apparatus during an actual treatment. Examples of such shield include a generally used Lipowitz metal shield and a multi-leaf collimator (MLC). In the case of a Lipowitz metal shield, it takes one or two days to manufacture an alloy block, whereas in the case of an MLC, no shield is manufactured and the MLC may be more easily manufactured into various irradiation surfaces compared to the alloy block. However, conventional MLCs are expensive and do not operate in association with various radiation devices.